1. Field of the Invention
The present invention relates to an electrostatic suspension device or levitator in microgravity or gravity conditions for a sample of material.
When producing materials in space by thermal and/or chemical processes, it is necessary in certain cases to obviate any contamination of the material that might be caused by physical contact with a holder or a crucible.
2. Description of the Prior Art
U.S. Pat. No. 4,059,797 filed Dec. 27, 1976, in the name of the assignee of the present application, discloses electrostatic suspension accelerometers in which the acceleration measurement is deduced from electrostatic forces required to hold a test weight in a position defined with respect to the body of the apparatus or to return said weight to this position.
Those accelerometers that are three-dimensional in nature comprise a floating spherical or cubic test weight and a set of electrodes, made up of at least two electrodes per unidirection. The electrodes both detect the position of the test weight and reposition said weight by slaving. The difference in capacity generated by two aligned electrodes and the test weight is measured applying an alternating current across the said electrodes and the resultant signal is processed in a proportional, integral, differential circuit which supplies repositioning signals back to the same electrodes.
In apparatus of this nature, the test weight can be steadied or stabilized only when the arrangement is three-dimensional and comprises at least six electrodes. Further, the potential on the test weight must be held equal to that of the apparatus body for maximum accuray.